Separation, isolation, and concentration are process steps common to a chemical analysis. Often, these steps are taken to remove interfering substances so that a subsequent chemical analysis can be performed. This separation stage can be performed in several ways including solvent extraction, solvent evaporation, and resin exchange. Magnetic separation, another technique for removing interfering substances, is a process of separation, isolation, and concentration where the sought-for substance is attached or bound to magnetic particles. The magnetic particles offer advantages of handling including speed, convenience, and low energy input. They are particularly suited to handling small samples.
In order to administer a magnetic separation, a threshold number of magnetic particles needs to be present in the solution to be measured. However, magnetic particles are more dense than most of the other particles in the solutions in which they are mixed. Therefore, the magnetic particles will accumulate at the bottom of their holding receptacles. Previous reagent cartridges for holding magnetic particle solutions or suspensions have used continuous mixing to ensure that appropriate concentrations of magnetic particles are distributed throughout the magnetic solution. However, continuous mixing can be expensive, inefficient, and prone to mechanical failures. The present invention addresses these shortcomings of prior art magnetic particle mixing tubes.